In "Assassin Marked," the locations are backdrops and not fully elaborated on in the story; however, Arbona and Penelope are advanced O'Neill Cylinders. Gerard K. O'Neill, an American physicist, proposed the design of these Cylinders, as conceptualized below.
By Rick Guidice NASA Ames Research Center - http://lifesci3.arc.nasa.gov/SpaceSettlement/70sArt/art.html, Public Domain, https://commons.wikimedia.org/w/index.php?curid=617874
If you've read "Assassin Marked," would you be interested in seeing it in a graphic novel form? If so, let me know in the comments below. As always, your input is appreciated!